Fiber-Optic Vibration Sensor for Physical Security System

Physical security technology is increasingly being used to prevent intruders from stealing or vandalizing property, leaking personal information, and threatening personal safety. Fences have been installed along the boundary of the premises of many public facilities to prevent any intrusion, and vibration sensors need to be easily fixable to these fences including around intricately shaped premises in order to adequately monitor a range of areas. Previously developed fiber-optic gyroscopes (FOGs), rotation sensors, and fiber-optic distributed temperature sensors (DTSs) are now used in various industrial systems, and if such well-established technologies can be applied to vibration measurement, it is reasonable to expect stable characteristics and reliability under severe environmental conditions such as the physical security and health-monitoring of a structure. A Sagnac interference system of FOG and an optical time domain reflectometer (OTDR) function of DTS have been investigated for their potential application to vibration sensing. The detection of vibrating position was also investigated for each type of sensor.